Many mobile computing devices, both small and large, utilize a touchscreen interface instead of a traditional keyboard as a primary means of user input. However, typical touchscreen interfaces alone generally lack the precision necessary to capture detailed drawings and/or writings such as cursive handwriting, annotations, sketches, or other detailed or nonstandard graphical input. To enable richer higher-fidelity user input, a stylus (or other writing-type device) may be utilized to improve the precision of a touchscreen interface for such mobile computing devices. A stylus can be readily used with a resistive touchscreen interface, an electrostatic (or capacitive) touchscreen interface, or an electromagnetic touchscreen interface.
However, current touchscreen interfaces—used alone or in combination with a stylus—lack the ability to enable three-dimensional (3D) user input. Consequently, traditional touchscreens are unable to support 3D interaction for purposes of playing 3D video games, using 3D computer aided design (CAD) programs, complementing other 3D user interfaces, or manipulating volumetric images such as medical imagery derived from MRI and CAT scans, among many other potential utilizations. Moreover, existing two-dimensional (2D) touchscreen user interfaces employ technologies that are unable to support broader utilizations for the provision of complementary mobile device applications such as position fixing and indoor navigation.